Many applications require high quality text or graphics like logos, UPC codes, lot numbers, prices, expiration dates, FDA/USDA nutritional statements, and other variable information to be printed on a substrate formed of flexible packaging films and rigid or semi-rigid materials. One of the printing technologies suitable for this type of printing is hot stamp imprinting, wherein a pigmented or inked ribbon and the substrate are compressed between a high temperature, thermal printhead and a pneumatically actuated backup assembly to transfer, or imprint, the pigment or ink from the ribbon onto the substrate. In the past, the efficiency of the imprinting process has been increased by including multiple printhead and backup assemblies to make a corresponding number of imprints on the substrate. In some applications, the available air supply, often supplied by a host packaging machine, limits the number and size of the printheads that may be operated at any one time. Prior art imprinters however do not provide means for controlling the air pressure supplied to the backup assemblies to ensure proper imprinting. In other applications, the printhead is reconfigured with different size print plates or steel type for printing lines of variable text, like expiration dates. The printheads of prior art imprinters however are not readily reconfigured and often require substantial disassembly to change the print plate or change the steel type. Further, changes in printhead configuration may require a change in air pressure for actuating the backup assembly to ensure proper imprinting and to prevent damage to the print ribbon and substrate. As discussed above, however, prior art imprinters do not provide means for controlling the air pressure supplied to the backup assemblies and therefore can not accommodate different printhead configurations without imprinter modification which often requires substantial disassembly. Prior art imprinters also have the disadvantage of requiring a considerable amount of electrical power for energizing the heater elements in the printheads and the print ribbon advance motor. Further, prior art imprinters often waste print ribbon. For example, during the imprinting process, prior art imprinters intermittently advance the print ribbon and the substrate between the one or more thermal printhead and backup assemblies, wherein the print ribbon is moved a fixed displacement interval, or increment, between imprints to position an unused portion of the ribbon between printhead and backup assemblies for the next imprint. Moving the print ribbon a fixed displacement interval between print strokes, however, does not efficiently utilize the ink on the ribbon, and results in significant ribbon waste. Also, during power down, print ribbon in prior art imprinters is often free to unwind from the supply reel which also results in unnecessary waste. Moreover, prior art imprinters do not monitor ribbon supply, or provide means for diagnosing the status of the imprinter.